A conductive film for electromagnetic deflection device

ABSTRACT

A conductive surface for an electromagnetic deflection device formed with helical, linear or zigzag gaps to thereby alter a current which flows through the conductive surface due to electromagnetic induction, thereby making possible a high frequency magnetic field within the device.

United States Patent Inventor Yoshihiro Uno Tokyo, Japan Appl. No. 740,340 Filed June 26, 1968 Patented Aug. 24, 1971 Assignee Matsushita Electric Industrial Co., Ltd. Kadoma-shi, Osaka, Japan Priority July 11, 1962 Japan 45176/42 A CONDUCTIV E FILM FOR ELECTROMAGNETIC DEFLECTION DEVICE 6 Claims, 3 Drawing Figs.

U.S. Cl..... 313/64, 313/75, 313/313 Int. Cl ..H0lj 19/40, H01 j 29/02 [50] Field ofSearch 313/64, 248, 313, 75, 83, 76; 335/212, 213, 214; 331/80; 328/229, 230, 231, 254, 255

[56] References Cited UNITED STATES PATENTS 2,569,654 10/1951 Cage .1 313/248 X FOREIGN PATENTS 682,302 3/1964 Canada 313/83 Primary Examiner- Roy Lake Assistant Examiner-V. Lafranchi A!torney-Stevens, Davis, Miller & Mosher ABSTRACT: A conductive surface for an electromagnetic deflection device formed with helical, linear or zigzag gaps to thereby alter a current which flows through the conductive surface due to electromagnetic induction, thereby making possible a high frequency magnetic field within the device.

PATENTED AUB24I97| 3,501,648

INVENTOR VDSHIH llO LL NO ATTORNEYS A CONDUCTIVE FILM FOR ELECTROMAGNETIC DEFLECTION DEVICE uniformly applied on the inner surface of the envelope at the position where deflection coils are located, thereby preventing an electric field from being established in that portion. For a relatively low electromagnetic deflection frequency, no problem will arise. However, as the frequency of a current which flowsthrough the deflection coils increases, such as on the order of IMI-I an induction current will be caused to flow through the conductive film on the envelope innner surface due to electromagnetic induction so that a magnetic field of high frequency will be prevented from entering into the tube. Thus, it will become possible to effectively deflect an electron beam.

Accordingly, it is an object of this invention to provide a deflection device which is capable of effectively establishing a high frequency magnetic field within a cathode ray tube by providing a conductive film with gaps rather than a uniform conductive film to thereby prevent an induction current from flowing through the conductive film.

Other objects, features and advantages of the present inven tion will be readily apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. I is a side view showing the main portion of the electromagnetic deflection device according to an embodiment of the present invention; and

FIGS. 2 and 3 are side views showing the main portions of other embodiments of the present invention.

Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

Referring to FIG. 1, the reference numeral 1 represents a glass envelope forming a cathode-ray tube, 2 a deflection coil, and 4 a deflection signal source by which a high frequency magnetic field is set up in the directions indicated by arrows 4.

The reference numeral 5 indicates a helical conductive film which is provided on the inner surface of the envelope in such a manner as to cover either the entire area which is under the influence of a magnetic field produced by the deflection coil 2 or the area corresponding to a relatively strong portion of the magnetic field. On the opposite sides of the spiral conductive film, there are provided uniform conductive films 6 and 7. By providing the helical conductive film at the position where the high frequency magnetic field is produced as described above, it is possible to produce a sufficient electrostatic shielding effect and effectively prevent an induction current.

In FIG. 2, there is shown another embodiment of the present invention wherein separate parallel bandlike conductive films are provided instead of the helical conductive film 5. That is, gaps 16 are formed between the bandlike conductive films. This embodiment is not so effective as the first embodiment using the helically wound conductive film, but a practically sufficient effect can be obtained.

By providing as shown in FIG. 3 the zigzag lacking portions 26 instead of the straight lacking portions, it is possible to more effectively prevent an induction current. In order to form conductive films of such a shape, the conductive film applying method for a post-acceleration type cathode-ray tube may be directly used for the embodiment of FIG. 1. In all of the above three embodiments, the same purpose can be achieved by vacuum-depositing metal through a mask of required shape, By the latter method, a conductive film of a complicated shape such as shown in FIG. 3 can easily be formed.

As described above, in accordance with the present invention, it is possible to effectively prevent an induction current which stems from a high-frequency magnetic field, thereb effectively establishing such high-frequency magnetic field within a cathode-ray tube.

The high-frequency electromagnetic deflection as described above can be utilized in an attempt to effect an electron-beam modulation type high-frequency wobbling deflection wherein an electron beam is deflected by a signal so that the electron beam density is modulated in accordance with the speed of deflection or to achieve high-speed marking or recording,

What is claimed is:

1. An induction current reducing device for an electromagnetic deflection device of a High-frequency magnetic deflection type cathode ray tube, comprising an insulating envelope defining a vacuum, high-frequency deflection coil means mounted on a part of the outside surface of said envelope, a conductive film coated on the inside surface thereof, and means reducing induction current flowing through the conductive film due to the high-frequency operation of said deflection coil means, including at least one nonconductive gap region provided in said film at a place which traverses the high-frequency deflecting magnetic field of said coil means.

2. An electromagnetic deflection device ofa high-frequency magnetic deflection type cathode-ray tube, comprising an insulating envelope defining a vacuum therein, said envelope defining a tubular portion through which an electron beam is directed, high-frequency deflection coil means mounted on a part of the outside surface of said tubular portion, a conductive film coated on the inside surface of said tubular portion and means reducing induction current flowing through the conductive film due to the high-frequency operation of said deflection coil means, including at least one nonconductive gap region provided in said film at a place which traverses the high-frequency deflecting magnetic field of said coil means.

3. An electromagnetic deflection device according to claim 2, wherein said conductive film is uniformly coated on said tubular portion.

4. An electromagnetic deflection device according to claim 2, wherein said nonconductive gap region has a helical form.

5. An electromagnetic deflection device according to claim 2, wherein said nonconductive gap region comprises a plurality of parallel band-shaped gaps with an equal distance therebetween.

2, wherein said nonconductive region has zigzag gaps.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent ,601,648 Dated Auqust 24, 1971 Inventor Yoshih-iro UNO It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Please correct the Claim for Convention Priority of the above application to read as follows:

--Japan, Patent Appln. N 45176/67 filed July 11, l967-.

Signed and sealed this 21st day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 1M PC405 uscoMM-oc 6037fl-P69 9 US. GOVERNMENT HUNTING OFFICE: IQII O-3II-I14 

1. An induction current reducing device for an electromagnetic deflection device of a High-frequency magnetic deflection type cathode ray tube, comprising an insulating envelope defining a vacuum, high-frequency deflection coil means mounted on a part of the outside surface of said envelope, a conductive film coated on the inside surface thereof, and means reducing induction current flowing through the conductive film due to the high-frequency operation of said deflection coil means, including at least one nonconductive gap region provided in said film at a place which traverses the high-frequency deflecting magnetic field of said coil means.
 2. An electromagnetic deflection device of a high-frequency magnetic deflection type cathode-ray tube, comprising an insulating envelope defining a vacuum therein, said envelope defining a tubular portion through which an electron beam is directed, high-frequency deflection coil means mounted on a part of the outside surface of said tubular portion, a conductive film coated on the inside surface of said tubular portion and means reducing induction current flowing through the conductive film due to the high-frequency operation of said deflection coil means, including at least one nonconductive gap region provided in said film at a place which traverses the high-frequency deflecting magnetic field of said coil means.
 3. An electromagnetic deflection device according to claim 2, wherein said conductive film is uniformly coated on said tubular portion.
 4. An electromagnetic deflection device according to claim 2, wherein said nonconductive gap region has a helical form.
 5. An electromagnetic deflection device according to claim 2, wherein said nonconductive gap region comprises a plurality of parallel band-shaped gaps with an equal distance therebetween.
 6. An electromagnetic deflection device according to claim 2, wherein said nonconductive region has zigzag gaps. 